The present invention relates to musical instrument, and relates more particularly to a coupling device for coupling two pedal mechanisms together permitting the beaters of the pedal mechanism to be separately driven to beat a base drum.
The pedal mechanism of a base drum is generally comprised of a pedal, a beater, and a transmission mechanism connected between the pedal and the beater. This structure of pedal mechanism can only beat the base drum intermittently causing the base drum to produce a monotonous sound. In order to play a fancy performance, two beaters are needed for beating the base drum. FIG. 1 shows a pedal system comprised of a first pedal mechanism and a second pedal mechanism linked by a link, a first beater pivotally mounted around a pivot shaft on the first pedal mechanism and driven by the pedal of the first pedal mechanism, and a second beater pivotally mounted on the first pedal mechanism by a coupling device and driven by the pedal of the second pedal mechanism. The coupling device, as shown in FIG. 2, comprises a circular rod section at one end having a circular hole and an axle bushing mounted within the circular hole and coupled to one end of the pivot shaft of the first pedal mechanism, and an coupling portion at an opposite end connected to the second pedal mechanism by the link. The second beater is perpendicularly connected to the circular rod section of the coupling device. Therefore, the first and second beaters can be separately driven to beat the base drum. This structure of coupling device is complicated and difficult to manufacture. The axle bushing must be precisely processed so that the coupling device can be smoothly turned relative to the pivot shaft of the first pedal mechanism. If the coupling device and the pivot axle are not precisely coaxially coupled together due to a small size error, the respective reciprocating motion of the first and second beaters will interfere with each other.